I sit in the upper deck and my complaint with the ushers is that for good stretches of the game they are nowhere to be found. So there are always people standing at the railing while the game is ongoing and there are people yelling at them to move since their home plate view is blocked.
I have noticed at other parks that the ushers are at the sections before the game starts and can direct you to your seat which is nice if you haven't been to the park before.

You can text a # that is found on the back on most seats to somewhat "tell on" people like this for ushers to come take care of. They can't be everywhere at all times.